محیط زیست، انرژی و رشد اقتصادی پایدار

Sustainable energy utilization and environmental protection are important to sustainable economic growth. In this paper, we develop an endogenous economic growth model and discuss the optimal path of sustainable economic growth with the constraints of energy and environment. We find that sustainable economic growth can be achieved only when the relative contribution rate of environment protection investment to environmental quality is more than the relative contribution rate of combined input of energy and environment to production. The results indicate that long-run growth requires not only a continuous energy intensity decrease and technology progress in the fields of energy resources exploitation, exaction, refinement and utilization, but also an optimal structure adjustment from depending on nonrenewable energy to renewable energy.

The sustainable energy utilization and the environmental protection are very important to sustainable economy and society development. In the past twenty years, many several developing countries have made amazing achievements in economic development. However, as concomitance of rapid economic growth and industrialization advance, the energy shortage and the environmental degradation poses a grave threat to the progress of industrialization and civilization. How to get mutual benefits between the energy development and environmental protection has drawn a lot of attention in the past twenty years. Whether can economy pursues the optimal growing path under the dual restraints of the energy and environment is the focus of sustainable growth.Exhaustible resources, mainly including nonrenewable energy and mineral resource, were once the focus of research work concerned with economy growth in 1970's. Quite a number of research works introduced exhaustible resources into neoclassic growth model and discussed the consequent influences on economic growth. They introduced the exhaustible resources into the Cobb-Douglas production function and tried to seek the relationship between the exhaustion of the natural resources and the long term economic growth. It was found that optimal distribution of exhaustible resources will take the intergenerational equity of the total wealth in a society into account and the sustainable development should be measured by total capital stock. Although the introduction of exhaustible resources into neoclassic growth pattern confirmed their restraint mechanism in as well as impacts on economy growth, the inherent contradictions in the neoclassic growth pattern was still left unsolved. Given Hicks neutral technical progress, the long term economic growth depends on the marginal factor income increasing, while the theoretical premise of the neoclassic growth theory was the marginal factor income decreasing. So, the decreasing marginal income led to an increasing resource exhausting rate. If the regenerating rate of resources cannot exceed the exhausting rate, economy would come to the zero growth inevitably. Since 1980s, some researchers developed new growth theory on the foundation of neoclassic pattern, which took the internal technique change as the core of economic growth and pay much attention to the knowledge overflow (P.M. Romer, 1986), human capital externality (R. E. Lucas, 1988), the new product introduction (G.M. Grossman, E. Helpman, 1991), learning by doing (Young and Allyn, 1991) and so on. By introduction of the knowledge and the specialized human capital, the new growth theory revealed that the human capital accumulation may cause an increasing marginal return as well as an increasing return to scale. Based on these theories, H. L Yang et al (2004) introduced energy into the Lucas endogenous growth model as a factor of production and discussed the function of the human capital accumulation in breaking out of the exhaustible energy reserve restraint. B. Yu et al (2006) introduced both energy exhaustion and environment protection into endogenous economic growth model and discussed the requirements of the sustainable growth. Omer and A Mustafa (2008) discussed several issues relating to renewable energies, environment and sustainable development from both current and future perspectives. Recently, some researchers attempt to use these models to anticipate the future of environment, energy and economy. For example, Z. G. Hu, J. H. Yuan and Z. Hu investigated the low-carbon development of China. According to their prediction of China's economic growth, energy reserves and emissions mitigation till 2030, China could save energy by more than 4 billion ton oil equivalences and reduce carbon dioxide emissions by nearly 17 billion tons during the coming 20 years. They also pointed out that China had to reconstruct its economy and depend much on technology progress in the future. These research works succeeded in introducing the energy and the environment restraints into the economic growth. Nevertheless, most of them only considered the negative impacts of environment, i.e. pollution, and little attention had been paid to the positive environment quality which could make contribution to the economic growth. Also little literature investigated the ability of environmental protection investment in improving environment quality. In the following sectors, we will introduce the energy and the environment into the production function and discuss the double influences of energy and environment and the optimal path of economic growth under these restraints.

In this paper, we develop an endogenous economic growth model with dual constraints of energy and environment. We find that with the restraints of energy and environment, economy growth can hardly be sustained without human capital accumulation, environmental protection investment or energy structure adjustment. Firstly, sustainable economic growth need an uninterruptable supply of energy, which can hardly been guaranteed with the limited reserve of exhaustible energy resources. Without technology progress, exploitation, refinement and utilization of exhaustible energy are not efficient enough to ensure energy structure change accomplished before we run out of fossil fuels. Secondly, environment investment is so important that the enlargement of economy scale will break the limit of environmental carry capacity sooner or later because self-regenerate rate of environment can hardly outpace the damage rate by economic growth without environmental recovery which is usually financial supported by government. Thirdly, change from depending on conventional fossil fuels to renewable energy is necessary because any technology advance cannot stop these energy resources from exhaustion eventually and negative effects to environment is often irreversible, or at least difficult to be eliminated or even mitigated. We also find that sustainable economic growth can be achieved only when the relative contribution rate of environment protection investment to environmental quality is more than the relative contribution rate of combined input of energy and environment to production. It implies that technology progress is not as important in environment recovery as it does in economic growth. Although there is no evidence, it can be reasonably inferred that technology advance in industrial emission control will bring more benefits to environment than it does in ecosystem restoration. Since so much environment deterioration is irreversible, financial support and scientific research should be directed to prevention rather than repairmen. All authors must sign the Transfer of Copyright agreement before the article can be published. This transfer agreement enables Elsevier to protect the copyrighted material for the authors, but does not relinquish the authors' proprietary rights. The copyright transfer covers the exclusive rights to reproduce and distribute the article, including reprints, photographic reproductions, microfilm or any other reproductions of similar nature and translations. Authors are responsible for obtaining from the copyright holder permission to reproduce any figures for which copyright exists.